wait a second -
there is no way water movement is going to increase the temperature of your tank - do you know how much energy it takes to heat the water in a 75 gal aquarium - its alot - so toss that idea.
the ciruclation of the filter should level the temperature throughout the tank and you are talking about a really big temperature difference. watch you heater and see if the light is turning on - it should not go on until the temp of the take drops below the level its set at.
Does your canister have a built in heater - some high end ones do?
What is the temperature of your house - by any chance 81 degrees?
there is no way water movement is going to increase the temperature of your tank - do you know how much energy it takes to heat the water in a 75 gal aquarium - its alot - so toss that idea.
the ciruclation of the filter should level the temperature throughout the tank and you are talking about a really big temperature difference. watch you heater and see if the light is turning on - it should not go on until the temp of the take drops below the level its set at.
Does your canister have a built in heater - some high end ones do?
What is the temperature of your house - by any chance 81 degrees?